linux-kernel - Re: [PATCH 2/8] arm64: dts: imx8mm-kontron: Make sure SOC and DRAM supply voltages are correct

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Message-ID: <cefc9a67-120e-fda6-cb69-af4cabc58a15@kontron.de>
Date:   Tue, 5 Oct 2021 15:10:14 +0200
From:   Frieder Schrempf <frieder.schrempf@...tron.de>
To:     Shawn Guo <shawnguo@...nel.org>, Frieder Schrempf <frieder@...s.de>
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>
Subject: Re: [PATCH 2/8] arm64: dts: imx8mm-kontron: Make sure SOC and DRAM
 supply voltages are correct

On 05.10.21 08:53, Shawn Guo wrote:
> On Thu, Sep 30, 2021 at 05:56:25PM +0200, Frieder Schrempf wrote:
>> From: Frieder Schrempf <frieder.schrempf@...tron.de>
>>
>> VDD_SOC should be 800 mV in suspend and 850 mV in run mode. VDD_DRAM
>> should be 950 mV for DDR clock frequencies of 1.5 GHz.
>>
>> This information is taken from the datasheet and the uboot-imx code.
> 
> I'm wondering where the existing settings were coming from?

Good question, but I can't really retrace now how I actually determined
the values back then. Seems like I had failed to validate them properly.

> 
>>
>> Signed-off-by: Frieder Schrempf <frieder.schrempf@...tron.de>
>> ---
>>  arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi | 6 ++++--
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi b/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi
>> index 03b3516abd64..b12fb7ce6686 100644
>> --- a/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi
>> +++ b/arch/arm64/boot/dts/freescale/imx8mm-kontron-n801x-som.dtsi
>> @@ -92,10 +92,12 @@ regulators {
>>  			reg_vdd_soc: BUCK1 {
>>  				regulator-name = "buck1";
>>  				regulator-min-microvolt = <800000>;
>> -				regulator-max-microvolt = <900000>;
>> +				regulator-max-microvolt = <850000>;
>>  				regulator-boot-on;
>>  				regulator-always-on;
>>  				regulator-ramp-delay = <3125>;
>> +				nxp,dvs-run-voltage = <850000>;
>> +				nxp,dvs-standby-voltage = <800000>;
>>  			};
>>  
>>  			reg_vdd_arm: BUCK2 {
>> @@ -111,7 +113,7 @@ reg_vdd_arm: BUCK2 {
>>  			reg_vdd_dram: BUCK3 {
>>  				regulator-name = "buck3";
>>  				regulator-min-microvolt = <850000>;
>> -				regulator-max-microvolt = <900000>;
>> +				regulator-max-microvolt = <950000>;
>>  				regulator-boot-on;
>>  				regulator-always-on;
>>  			};
>> -- 
>> 2.33.0
>>